Systems are known to provide power in the event of failure of a power grid. Such systems may have operational characteristics based upon the equipment powered and/or upon any of a number of other support requirements. For example, where short periods of power outage may be tolerated, then a gasoline or diesel powered generator or alternator may be activated following the power failure.
Other systems may rely upon the use of one or more batteries to provide power. This may be a useful alternative where an internal combustion engine cannot be used because of safety concerns or because of space limitations.
However, a battery may provide a power output at a single direct current voltage while the load may require an alternating current voltage. This may require the use of a power converter that converts the direct current of the battery to the alternating current of the load.
In order to facilitate the powering of equipment from a battery, a number of different power converters may be used. For example, some backup systems have used direct current (dc) motors powered directly from the battery to mechanically drive an alternating current (ac) generator that is, in turn, used to provide ac power to the computer system. Other systems have relied upon the use of solid state inverters to convert the dc power of the battery to the ac power required by some types of computer equipment.
An inverter may include one or more switches that interrupt the battery voltage at a predetermined frequency (e.g., 60 Hz). The result is a waveform that roughly approximates the sine wave of ac power normally received from the power grid.
While inverters work relatively well, it is sometimes difficult to match the load to the switching capabilities of the inverter. Accordingly, a need exists for better methods of generating ac during power failures.